Expansive bit.



H 0. DAVIS. EXPANSIVE BIT.

APPLICATION FILED JUNE 3,1915.

Patented Dec. 28, 1915.

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HENRY O. DAVIS, 01? GLOUCESTER, MASSI-KCHUSETTS, ASSIGNO'B, I0 DAVIS HARDWARE MANUFACTURING COMPANY, OF GLOUCESTER, MASSACHUSETTS, A CCiR-PORA'IION OF MASSACHUSETTS.

EXPANSIVE BIT.

Application filed June 3, 1915.

To all whom it may concern Be it known that l, HENRY O. DAVIS, a citizen of the United States, residing at Gloucester, in the county of Essex and State of Massachusetts, have invented an Improvement in Expansive Bits, of which the following is a specification.

The ordinary expansive bit, or wood auger, which has been in general use for many years, comprises a main auger having a fixed blade thereon, and a second blade which is mounted for radial adjustment in a slot in the shank of the auger and is adapt ed to remove a chip beyond that removed by the main auger. While these bits are suit able for boring holes approximately 2-1,; in. in diameter, and less, if the wood is hard, or if it is attempted to bore a hole of greater diameter, the strain on the adjustable blade is so great at the point Where it extends beyond its seat, that it is liable to be broken off at this point. Moreover, the strain on the bit, at the side from which the blade projects, is much greater than the strain at the other side, so that there is a tendency to cause the bit-shank to be tilted out of alinement, and, when this occurs, the danger of breakage is greatly increased, and the boring of a uniformly round hole is pre vented.

The object of my invention is to provide a form of expansive bit, with which holes may be bored which are of considerably greater diameter than the holes which it has previously been possible to bore,"with the ordinary expansive bit, above referred to, without breaking it, and with which, at the same time, will operate in the manner of an ordinary wood auger, in that it will bore a hole to the full size desired from the beginning of the operation to the end, and incidentally will obviate the tendency to cause the bit-shank to be tilted out of line. 1 accomplish this object, primal-1y, by providing the shank of the bit with a pair of blades, at opposite sides thereof, which project unequal distances radially from the center. and

by arranging said blades so that the cutting edge of the shorter blade will be held a short distance, equal the depth of a chip, in advance of the edge of the longer blade, so that the longer blade will only engage the wood outside the path of the end of the shorter blade, thereby equalizing the strain on the blades, so that neither will be unduly Patented Dec. 2%, 1915.

Serial No. 31,975.

strained, and preventing the strain of cutting the wood, beyond that cut by the main auger, from being placed entirely on one blade.

For a more complete understanding of my invention, reference is made to the accompanying drawing, in which,

Figures 1 and 2 are elevations of a bit or auger made according to my invention. Fig. 3 is a longitudinal, sectional view on the line 3-3 of Fig. 1. Fig. 4c is an end view of the hit.

As shown in the drawing, the shank a, of the main portion of the bit, is provided with the usual fixed cutting blade 6 at its lower end, and with the usual feeding worm 0.

According to my invention, 1 provide a pair of blades (Z and c, which are similar in form to the ordinary adjustable blade employed in the common form of expansive bit, except that the blade 0 is of substantially greater length (approximately onethird greater, at least) than the blade cl, which is of usual length. I further provide means for clamping said blades at opposite sides of the shank, and for this purpose dovetail shaped grooves are formed in the opposite sides of the shank, the bottoms of which are flattened, to provide fiat seats for the inner sides of said blades cl and e, under-cut shoulders f and being formed at the sides of said grooves next the blade 6, and under-cut shoulders h and 2' being formed at the opposite sides thereof. The edges of the blades, which carry the cutting edges, are formed to fit against the upper side of the blade Z) and are inwardly inclined to fit against the shoulders f and 9, while the opposite edges are outwardly inclined, to receive correspondingly inwardly inclined edges of a pair of clamping plates 7' and 70, respectively, the opposite edges of the latter being outwardly inclined, to engage the shoulders h and 2'. A clamping screw on is arranged to pass through plate der f is somewhat lower, or nearer the threaded end of the bit than the shoulder g,

this difference preferably corresponding, approximately, to the pitch of the threads on screw 0. As a result, when the blades are placed in position, the cutting edge d, of the shorter blade (Z, will be held in advance of, or at a slightly lower elevation than the cutting edge e, of the longer blade 6, said edge d being held approximately midway between the edge of the blade Z) and'the edge e, at the point where said edges cl and a leave the side of the shank a.

The blades (Z and eare so formed'and' the seats in which said blades are held are so located, that their cutting edges extend downwardly as they extend outwardly, to such an extent that the outer ends of the blades (Z and 6 will be each carried at approximately the level of the fixed blade I), or in the plane of its path, so 'thatthe fixed blade and the longer blade will cut through the wood at the same time. It may be noted in this connection, that with a-boring tool of this type, it is practically essential that all the blades operate at approximately the same level, or closely adjacent the level of the shank end of the feeding worm, otherwise the hole would not be bored through the wood, throughout its entire diameter, by the time the worm passed therethrough, and became ineffective to feedthe tool.

In practice the longer blade 6 will be set to out a chip having the full diameter of the hole to be bored, while the shorter blade (Z will be set so that its'outer'end is approximately midway between the outer end: of the shank blade Z) and the outer end of' the longerblade 6. When the partsarethus set, the following operation will take place in boring'a hole: The blade 6 will first remove a chip in advance of the engagement of the blade (Z with the wood, then the portion of the edge of the blade cl, extending beyond the body of the auger, willl next engage the wood, and will remove a chip having awidth corresponding to the distance which it projects beyond the blade Z) and having a thickness, or depth equal to the pitch of the thread a. The portion of the blade 0 which extends beyond the end of the path of the endof the blade (Z, will next engage'the wood and remove a similar chip, having a diameter equal to the diameter of the hole, but the wood which would have been otherwise removed by the edge-portion within the path of the end of the blade (Z will have been removed by the latter, so that the chip removed by blade 6 will be of no greater width than the distance from the path of the end of the shorter blade to the path of the end of the longer blade. The strain of boring which is placed on the-bladesiis thus equalized to such an extent that neither blade (Z or 6 has an unduestrain placed thereon. The danger that the longer blade will becbroken when boring a largehole is thus to a large extent, avoided, and, as the strains are nearly equalized, at opposite sides of the shank, there will be but slight tendency to prevent the bit from running true.

In practice three or more bits, all of differentlengths, but all interchangeable, may be provided, so: that the advantages of the above described construction may be secured in boring a hole of comparatively small diameter, as well as in boring one of large diameter, this being accomplished by emthe threads of the worm, Iamable to satisfy all the requirements ofan ordinary-expansive bit, or wood auger, whileat the same time, I -make itpossibleto bore holes of much greater diameter than may be bored 'withiany other expansive bit, or wood-auger of which I" a-mi aware, and, other conditions being equal, todothis without increasing the danger of the. blades being broken-by undue strain-..

I- claim p -1. A wood anger comprising a: shank having a-feedin-g worm at its end, a pair of blades mountedon said--sha-nk-adjacent its worm and having their cuttingedges extending therefrom to difierent radial dis,- tances, the blade extending to the shorter radial distance. having its. cutting edge arranged inadivance off that of. the other blade by' approximately the distances between two of the threadsof vthe worm. I

2.. A. wood auger: comprising a shank' having' a. feeding worm atits'end, a pair of blades mounted for radial adjustment on theshank with their cutting edges-extending from points adjacentthe end of the shank to different radial distances, the blade of shorter radius being disposed;- sufficiently in advance of the other blade'to remove the chip which would otherwise be removed by the corresponding portion of the longer blade.- I

3. A wood auger comprising-a shank having a feeding worm on its end, a pair of blades mounted for radial adjustment on opposite. sidesof the shank and having; their cutting edgesextending from points adjacent theend: of the shank to different radial Vance of the corresponding portion:of the other blade to prevent operative engagement of such portion with the work.

4. A wood auger comprising a shank having a fixed blade and a feeding worm at its end, a pair of blades mounted for radial ad-' justrnent on opposite sides of the shank and having their cutting edges extending radially and obliquely from points adjacent and above the path of said fixed blade, approximately to the plane of said path, one of said blades extending to a substantially less radial distance than the other and having its cutting edge disposed sufiiciently below the path of the corresponding portion of the other blade to prevent operative engagement of said portion with the work.

5. A bit-shank having a blade at its end and transverse blade-receiving grooves at opposite sides, clamping plates arranged to engage corresponding sides of said grooves, blades arranged to be engaged at opposite edges by said plates and by the opposite sides of said grooves, and a clamping screw arranged to draw said plates into clamping engagement with said blades.

6. A bit-shank having a blade at its end and transverse blade-receiving grooves at opposite sides, clamping plates arranged to engage corresponding sides of said grooves, blades arranged to be engaged at opposite edges by said plates and by the opposite sides of said grooves, a clamping screw extending through one of said plates and said shank, and threaded in the, other plate, to draw said plates into clamping engagement with said blades to lock them in said grooves.

In testimony whereof, I have signed my name to this specification.

HENRY O. DAVIS.

Witness L. H. HARRIMAN.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. O. 

